A Level Biology Revision Notes

Comprehensive A Level Biology revision notes providing information and assistance for all UK examination boards (AQA, OCR, Edexcel) as well as international curriculum (CIE).

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Structures of Blood Vessels

Summary The main artery in the heart is the aorta and arteries carry blood away from the heart Arterioles are smaller arteries that diverge into capillary beds Exchange of nutrients, waste and oxygen occur at the capillaries within tissues at cellular level Veins are blood vessels that return blood back to the heart; where venules …

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Dipoles Of Water Molecules

Summary Water is the main constituent in all organisms A water molecule is said to be dipolar because it has a positive and a negative pole as a result of the uneven distribution of electrons within it The dipole nature within a water molecule creates attractive forces known as hydrogen bonding, allowing them to stick …

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Summary To ensure that blood vessels don’t break when there is a cause of injury, a blood clot is crucial Blood clotting can also prevent you from bleeding to death which also protects you from bacterial and virial infection The process by which a blood clot is formed is called the coagulation cascade that involves …

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Transport In Animals

Summary Transport of materials i.e nutrients and gaseous exchange is basic necessity of living organisms Unicellular organisms transport materials via active and passive transport Multicellular organisms require a complete system of transportation called circulatory system Passive transport is carried out either by diffusion or by osmosis process Passive transport does not require energy Active transport …

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Difference between monosaccharide, disaccharide and polysaccharide

Summary The three types of carbohydrates are monosaccharides, disaccharides and polysaccharides Monosaccharides are the simplest sugars e.g. glucose. fructose and galactose Disaccharides are formed by condensation where there is linking of two monosaccharides together Disaccharides can be broken down to monosaccharides via hydrolysis Polysaccharides, also known as polymers contain three or more monosaccharides Polysaccharides; starch, …

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The Mammalian Heart

Summary The heart is a muscular organ in majority animals that pumps bloods via the blood vessels to form the circulatory system Blood provides the human body with important nutrients and oxygen whilst also assisting in the removal of metabolic waste The heart is situated off centre to the left side of the rib cage …

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The Cardiac Cycle

Summary The sequence of one heart beat ending to the beginning of another is known as the cardiac cycle The heart consists of two pumps that work together where both sides of the heart relax and contract with one another Systole is the repetition in contractions of the heart chambers Diastole is the relaxation of …

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Summary Atherosclerosis is a progressive disorder and primarily an inflammatory disease It is caused by atheroma’s and marked by the narrowing of arteries by the hardening done by plaques Atheroma is the flaky material made up of lipids (cholesterol and lipid), macrophages, calcified lesions and fibrous tissue that are present nearest the lumen of an …

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